The present invention comes out of work in the production of phenate-stearates having a high Total Base Number (TBN).
European Patent Application No. 0,094,814 A2 teaches improving the stability of an overbased phenate by treating the phenate with a carboxylic acid having a C.sub.10 to C.sub.24 unbranched segment, such as stearic acid.
PCT Patent Applications WO 88/03944 and 88/03945 teach an overbased phenate having a TBN of more than 300. This high TBN is achieved by using an additional component: either a carboxylic acid, such as stearic acid, or a di- or poly carboxylic acid having from 36 to 100 carbon atoms, or an anhydride, acid chloride, or ester thereof.
U.S. Pat. No. 5,728,657 teaches a process that produces an overbased sulfurized phenate-stearate without producing fine sediments. That process controls the degree of agitation and the ratio of ethylene glycol to water during the overbasing process to prevent the formation of fine sediments.
In the production of highly overbased phenates (TBN's in the range of 300 to 450) and even less overbased phenates (TBN's in the range of 150 to 280), the viscosity of the product is an important concern. If the viscosity is too high, it becomes difficult or impossible to handle, pump, filter, or store the product.
There have not been a large number of techniques or methods for lowering the viscosity of highly overbased phenates. However, in European Patent Application No. 0,094,814, the addition of long chain carboxylic acids during phenate processing was found to "result in valuable reduction in viscosity of oil solutions of the additive". This approach has also been disclosed in U.S. Pat. Nos. 5,069,804; 5,162,085; 5,716,914; 5,714,443; and 5,728,657.
In the preparation of what can generally be considered "fatty-acid" modified phenates, such as disclosed in the patents cited above, calcium chloride is sometimes added to the phenate process. For example, solid calcium chloride is used in U.S. Pat. Nos. 5,716,914; 5,714,443; and 5,728,657.